GFDL-CICS effort improves oceanic overflow representation in climate models
Several new parameterizations of overflow processes, including the flow through narrow gaps, entrainment of overlying waters and frictionally-induced mixing at topography, have recently been implemented in the ocean models developed at the Geophysical Fluid Dynamics Laboratory (GFDL), leading to significant improvements in the simulated ocean circulation. These parameterizations are described in a recent Bulletin of the American Meteorological Society publication (Legg and co-authors, 2009, doi:10.1175/2008BAMS2667.1). This improvement in ocean climate models results from the efforts of the Gravity Current Entrainment Climate Process Team (http://www.cpt-gce.org), a five-year collaboration between climate model developers, and researchers conducting observational, numerical and laboratory process studies of overflows, led by Cooperative Institute for Climate Science (CICS) researcher Sonya Legg.
Background: Oceanic overflows are bottom-trapped density currents originating in semi-enclosed basins or on continental shelves. They are the source of most of the abyssal waters of the ocean, and play an important role in the large-scale ocean circulation. Historically, overflows have been poorly represented in climate models, since most of the active processes occur well below the climate model grid-scale. As a result deep waters are not simulated correctly, leading to errors and uncertainties in the climate simulation. The climate process team was established by the US Climate Variability and Predictability Research Program (US CLIVAR) to address this problem, and includes members of CICS, and NOAA-GFDL, as well as other partners at the National Center for Atmospheric Research and in academia. The climate process team is jointly funded by the National Science Foundation and NOAA.
Significance: Improved representation of overflows in climate models, developed through a close collaboration between academia and modeling centers, is leading to better fidelity in climate simulations, and hence more credible climate change projections, supporting NOAA's climate goals. This research supports NOAA Mission Goal 2 - Understand Climate Variability and Change to Enhance Society's Ability to Plan and Respond.